Timing's off on my New Home 632?

Hi, I have a New Home 632 which has never behaved well since I was given it. Gradually, it has become worse and worse for skipping stitches, breaking needles, jamming up with bunches and bunches of the lower thread wedged underneath the needle plate. I have fiddled with both the top thread and bobbin tensions, and cleaned and oiled the machine. This hasn't helped, and I think this just leaves the timing. I've seen general guidance for how to set this on most machines, but I can't find anything specific to this model. Any body know what sort of distance between the hook and the needle's eye I should be starting off with?